Evolution as Metaphor


Biological evolution is controversial, but it at least has the imprimatur of science. The same cannot be said for all the ways in which evolution has infected our thinking about everything from sociology to economics. For example, it has become common to refer to almost any kind of progress as evolution. We might talk about the evolution of the computer or the evolution of a software application. In doing so, we tacitly remove intelligent intention from the understanding of progress. Evolution purports to describe a process by which all living things arose from inanimate matter with only three principles to drive it: 1. sufficient time (billions of years) to make highly improbable events likely, 2. a mechanism of variation (mutation), and 3. a mechanism to drive toward increasing complexity (natural selection). There is no intelligence (or at most a very minimal intelligence) in this process and certainly no intention.

Proponents of intelligent design don’t find these three principles sufficient. It’s not hard to see why. The first principle is not controversial. If I flip a coin 20 times, the chances that it will come up heads every time are a bit less than one in a million. If I flip a coin 1,000,000 times, though, the chances of having a string of 20 heads somewhere in there is a bit more than 60%. If I flip the coin billions of times, the chances of a string of 20 heads approaches certainty. The probability of life arising from non-living matter is considerably smaller by several orders of magnitude. Scientists have been unable to produce any self-replicating organisms from lifeless matter despite doing their best to stack the odds in their favor.

Mutation is also not controversial. Everyone agrees that mutation occurs, and has a variety of causes. There is one little sticking point, however. Nearly all mutations that we have been able to cause or observe make a species less likely to survive, not more likely. The odds against a variation caused by mutation being useful are very high, and they become higher still the more complex the organism is. Moreover, in mammals at least, mutations that significantly alter an individual often leave it sterile. Mutation may be necessary for evolution, but it hardly seems sufficient to expalin the actual diversity of life.

Natural selection is by far the most controversial and least observable of the drivers for evolution. The idea seems simple enough. Individuals well-suited to their environment will thrive and reproduce. Ill-suited individuals will die, and with them the genes that make them ill-suited will be lost. One commonly cited example is that of the peppered moth. During the industrialization of Britain, pollutants darkened the trees where the peppered moth commonly rested. Most moths were light colored, and birds could easily spot them against the soot-stained bark of the trees. After a few years, most peppered moths were dark; the light variety had all but vanished. As time passed, Britain cleaned up its pollution. The trees were no longer stained by soot, and the bark became lighter. The color of the moths changed again from dark to light.

The problem with this example is twofold. It does not demonstrate a change in the genetic makeup of peppered moths, only in the characteristics of a population. Nor does it provide the kind of dramatic change that must occur for natural selection to be a sufficient driver for evolution.

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11 Responses to Evolution as Metaphor

  1. Matt Brinkman says:

    Chip wrote, “Speciation does not occur by gradual, minute changes (at least not if the fossil record is any indication). New species appear quite suddenly with a startling absence of transient forms.”

    The British herring gull can successfully interbreed with gulls of the american eastern seaboard. These american gulls can successfully interbreed with Alaskan gulls, which can interbreed with Siberian gulls. Following through interbreeding populations, we loop all the way back to England. “So what?” you may ask.

    As one moves away from Britain towards the west, the gulls get smaller and develop darker coloration. By the time the loop closes in Britain, you have two distinct groups of birds. These populations look markedly different and are incapable of interbreeding–by common definition these two populations on Britain are distinct species.

    Until we close the loop, the various populations exhibit gradual minute changes (so minor in fact that the overlapping populations can interbreed). By combining enough of these gradual minute changes, however, we reach the point that we have (essentially) two different gull species. There are other well studied examples of the “ring species” phenomenon.

    Chip, you are quick to point out that you have not argued that evolution does not take place. What you have done, however, is posited that there is some fundamental barrier of “too much” change that evolution cannot bridge. Precisely how much change do you feel is “too much” for evolution to explain and what physical mechanism are you proposing to enforce this constraint?

  2. Chip Burkitt says:

    Matt, I haven’t argued that evolution does not take place. I’ve only argued that the three drivers (time, change, and natural selection) are insufficient. I take the changes in the peppered moth (and similar examples, such as antibiotic resistance in bacteria) as illustrations that even if natural selection occurs, it is still an insufficient driver for speciation. None of the changes mentioned are significant enough to account for the tremendous complexity and variety of living things on the earth. Speciation does not occur by gradual, minute changes (at least not if the fossil record is any indication). New species appear quite suddenly with a startling absence of transient forms. This is a fact which the theory of evolution has not adequately dealt with.

  3. Matt Brinkman says:

    Chip wrote, “Since evolution has taken such hold on the postmodern consciouness, we should understand what an evolutionistic understanding of life really means, beyond the science.”

    That’s because the Peppered moth example is a living demonstraion of evolution via natural selection. As you stated originally changes to the underlying genetic options is the result of mutation (you should have added genetic drift).

    If you want examples that demonstrate both mutation and natural selection, there are any number of examples that can be provided. Of high current interest would be any of the numerous cases studied of the emergence of anti-biotic resistent bacteria.

    This “argument” against evolution does nothing more than demonstrate the arguer is confused about what the peppered moth example shows.

  4. Chip Burkitt says:

    Josh, I think creation science (if there is such a thing) has problems, too. One non-scientific possibility is that God created the universe a short time ago but with a history. Just as an author may right a book about adult characters in a world with a history all its own, God may have created the universe beginning at a certain moment but having a history that predates the moment of creation. There are two big problems with such a theory: 1) It is not falsifiable. 2) God appears as a deceiver because he hides his own creative act behind a history that “never happened.” (The quote marks are needed because even though God created the history after it happened, it’s still real because God created it.) Clearly, such a view requires too much convoluted thinking. Another possibility is that the creation stories in the Bible were not intended to provide a modern scientific explanation of the processes by which everything came to be. Instead they are intended to show that everything that exist was created by God, who made everything according to a plan and with definite purpose. This is a view which does not contradict biblical theology and may not contradict science as long as the science is also rightly understood. Kierkegaard once wrote that when you reach a contradiction, a task for understanding remains. In other words, if the Bible is true, and science is also true, and they contradict, then we have not yet rightly understood the Bible or the science or both.

  5. Josh Belcher says:

    The theory of evolution fascinates me. First I would like to say that I am a Protestant born-again Christian and have been that for eight years now. Before that, I was an agnostic/atheist who believed in the theory of evolution and that the existence of the universe did not necessarily require a supernatural origin. Now I do. However, I still wonder if the theory of evolution holds some credibility. Now, I know that if one believes in the Authority of Scripture (such as myself) there are problems with that, but just because a theory has problems doesn’t mean that it isn’t valid and that one day those problems will not be conclusively resolved. So is evolution guided by God valid? I am not yet convinced if the theories of Creation Science are superior to the theories of Evolutionary Biology. To me, it seems that there is much evidence in favor of evolution. It seems that the argument for a young earth seems to imply that, given enough time, macroevolution would be possible.

  6. Mark says:

    Regarding the discussion of the English peppered moth, the predators that would primarily function to diminish population of the moths do not locate their prey with reference to a dark (or light)tree. The greatest majority of these moths are eaten while flying, by birds and bats. I don’t know if anyone has yet found an adequate explanation for the change in light/dark moth populations, but my guess is that some other environemental or genetic factor (probably a combination of the two) is involved. Much more salient to your discussion are the questions as to whether or not enough time has elapsed (since the begining of the universe) to allow for abiogenisis to account for the existence of life, and whether random mutations on existing populations are likely lead to radical increases in phyisiological complexity that intraspecial progress demands. I have not seen any convincing evidence answering either of these questions in the affirmative.
    Rant on, Bro!

  7. Chip Burkitt says:

    My point is that a change in the characteristics of a population may or may not reflect changes in heritable traits. It could be solely due to environment. In the case of peppered moth, I don’t think a change in heritable traits has been demonstrated.

  8. Matt Brinkman says:

    Chip, I guess I am confused as to what exactly you think biological evolution is. You wrote, “The problem with this example is two-fold. It does not demonstrate a change in the genetic makeup of peppered moths, only in the characteristics of a population.”

    In the mid-1930 biologists merged the Darwinian natural selection with Mendelian genetics to produce what is known as the modern synthesis. “The modern synthesis understands evolution to be a change in the frequency of alleles within a population from one generation to the next.” [Cite] (An allele is a heritable trait.)

    Now it turns out that the coloring of peppered moth offspring is imperfectly linked to the coloring of their parents. This means, for example, that light-colored peppered moth parents will produce children that are predominantly light-colored. As such, as “off-colored” parents are eaten, a lower percentage of “off-colored” offspring are born, which means the popluation change caused by the mechanism of natural selection is passed onto subsequent generations via the mechanism of heredity.

    By definition, heritable changes in the characteristics of a population is evolution.

  9. Chip Burkitt says:

    Matt, I know natural selection has no preference for complexity, yet we are to believe that complexity occurred from just the three drivers I mentioned (eons of time, change by mutation, and natural selection).
    The point of the peppered moth example is that no actual winnowing (at a genetic level) occurred. The population of light moths recovered very rapidly. The only mechanism at work was that moths that contrasted with their background tended to get eaten, so there were fewer of them.

    You’re absolutely right about my confusing abiogenesis and evolution. I am a layman with a layman’s understanding of what’s involved. Regardless of what terms are used, both abiogenesis and evolution have difficult problems with them. I’m not saying they’re wrong, just that if they’re right, something is missing from current explanations.

  10. Nick says:

    Great post Chip. I agree! What a great presentation of the shortcomings of evolution.

  11. Matt Brinkman says:

    Just three quick conceptual clarifications:

    1) Natural selection is not “a mechanism to drive to complexity.” Natural selection is a mechanism to drive a population to increased “fitness within an existing environment.” It has no preference towards increasing, decreasing, or leaving unchanged the level of complexity.

    2) The discussion of the peppered moth is slightly muddy. Changes in genetic make-up arise from mutation (and isolation). They are not expected to arise from natural selection which is, in general, a winnowing process.

    3) This post confuses abiogenesis and evolution. Abiogenesis deals with the emergenece of life from non-life. Evolution deals with the changes in allele (heritable trait) frequencies within a population.

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